This invention relates generally to facsimile machines and, more particularly to a facsimile machine adaptable to digital synchronization FAX protocols, including the MIL-STD-188-161 B&C standard.
Facsimile machines are used to transmit and receive image data over a communication link in accordance with pre-determined protocols that can include two operation modes: (1) a non-handshake mode, and (2) a handshake mode. The MIL-STD-188-161 B&C standard defines such two operation modes.
Handshaking refers to a bilateral information exchange between a transmitting facsimile machine and a receiving machine, that can facilitate data transmission. In non-handshake mode, no such handshake information is required for a facsimile machine at the transmitting end of the communication link to send FAX or image data to a facsimile machine at the receiving end of the communication link. By contrast, in handshake mode to initiate image data transmission from the transmitting facsimile machine, such handshake information is required between facsimile machines at the transmitting end and at the receiving end.
Traditionally, being adaptable to a pre-determined protocol that includes both non-handshake and handshake modes, the facsimile machines at the transmitting end and at the receiving end both have to be set in the same mode (either both in a mode for non-handshake operation or in a mode for handshake operation). This is so because in non-handshake mode (or broadcast mode) the transmitting end blindly transmits image data and assumes that the receiving end is ready and can comprehend the image data. In handshake mode, however, the transmitting end first sends a beginning protocol; in response to which, the receiving end has to send a response indicating its readiness and capability to accept the image data. Thus, in handshake mode, the transmitting end has to wait and verify this response before transmitting image data.
Under certain applications, a protocol that includes the both operation modes is required. For example, the MIL-STD-188-161 B&C standard is mandatory within the Department of Defense in the design, development and acquisition of facsimile equipment. (For detailed information of the MIL-STD-188-161 B&C standard, see the MIL-STD-188-161 B&C specification entitled "Interoperability and Performance Standards for Digital Facsimile Equipment" published by the Department of Defense, Washington, D.C.)
Conventionally, if the two facsimiles at the transmitting end and the receiving end are set in different modes, the image data may not be correctly transmitted. For example, assume that the facsimile machine at the transmitting end is set in handshake mode, and the facsimile machine at the receiving end is set in non-handshake mode. After transmitting the beginning protocol to the facsimile machine at the receiving end, the facsimile machine at the transmitting end awaits a confirmatory response from facsimile machine at the receiving end. But if the facsimile machine at the receiving end is set in non-handshake mode, it will never issue the response. As a result, the facsimile machine at the transmitting end cannot start image data transmission.
Clearly then the restriction that the facsimile machines at the transmitting end and the receiving end must be set in the same operation mode can be disadvantageous. To ensure an ability to receive image data transmitted in either non-handshake or handshake mode without interferences, the receiving end should have two facsimile machines with one being set in non-handshake mode and the other being set in handshake mode. Alternatively, using one facsimile machine to receive image data transmitted in either operation mode would require the receiving end to manually re-set its facsimile machine according to the operation mode changes at the transmitting end.
Thus, there has been a need for a facsimile machine whose operation mode can be automatically set and re-set to match the operation mode at the transmitting end. Such facsimile machine should also adapt to existing protocols, including the MIL-STD-188-161 B&C standard. This invention provides such a facsimile machine and a method to meet this need.